Optimization of organ culture conditions using rat colon so that the duration of in vitro experiments can be extended beyond a few weeks. In previous reports, we have established methods for culturing newborn rat and hamster colon. The specific aim of this study will be to establish better culture conditions, using our technique as a basis, for long term culturing of adult rat colon. Investigation, in organ culture, of various aspects of lesion developmand and metabolism subsequent to treatment with known or suspected carcinogens, co-carcinogens, and promoters. Performance of similar studies on explants of rat colon transplanted to whole animals. Investigation of lesion development and metabolism of colonic explants immediately transplanted to host rats and subsequent treatment with suspected carcinogens.